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Biomedical subjects

P Reid

Publications and source records attributed to P Reid.

At least 73 records · Page 4Linked to original sources
PubMed1979

Alterations in ventilation and gas exchange during exercise-induced carbohydrate depletion.

The relationship between ventilation (VE), oxygen consumption (VO2), and carbon dioxide production (VCO2) during work were studied in four trained males during exercise-induced carbohydrate depletion. Repeated bouts of heavy treadmill exercise (6 min at 95% VO2 max) were performed once per hour for 24 h in order to promote a shift in energy substrate from carbohydrate to fat. Measurements of VO2 and VCO2 recorded during each minute indicated that VO2 was unaffected by the number of runs, whereas VCO2 showed a progressive reduction which amounted to 24% during the final run. A corresponding decline of 19% was observed in the respiratory exchange ratio. No significant change in VE occurred between any of the runs. It is concluded that during heavy, repeated, muscular exercise, reductions in VO2, strongly suggestive of an increased fat oxidation, are not accompanied by a corresponding change in ventilation.

Adult↗
PubMed1977

Differential effect of hypophysectomy on the synthesis of beta-glucuronidase and other androgen-inducible enzymes in mouse kidney.

The levels of several androgen responsive enzymes including beta-glucuronidase, alcohol dehydrogenase, D-amino acid oxidase and arginase, were compared in kidneys of normal and hypophysectomized female mice after treatment with testosterone. While hypophysectomy did not alter the basal level of glucuronidase, the androgen-mediated accumulation of kidney beta-glucuronidase was greatly decreased in hypophysectomized mice. Measurements of the rate of synthesis of glucuronidase showed that after androgen treatment the enzyme was synthesized in kidney of hypophysectomized mice at only 5% the normal rate. Glucuronidase activity in seven other organs was not appreciably affected by treatment with androgens or by hypophysectomy. Unlike the effect of hypophysectomy on kidney glucuronidase, there was no reduction in the accumulation of alcohol dehydrogenase or D-amino acid oxidase in kidney of hypophysectomized mice after androgen treatment. Hypophysectomy caused a large reduction in kidney arginase activity. However, subsequent administration of testosterone restored much of this activity. It is concluded that there are at least two mechanisms by which androgens increase enzyme activity in kidney. The normal increase in activity or rate of synthesis of beta-glucuronidase following androgen administration requires pituitary hormones and/or products of these hormones, while the increase in activity of enzymes like alcohol dehydrogenase and D-amino acid oxidase does not require pituitary hormones.

Adrenalectomy↗
PubMed1970

Rifampicin inhibition of ribonucleic acid and protein synthesis in normal and ethylenediaminetetraacetic acid-treated Escherichia coli.

The kinetics of ribonucleic acid (RNA) and protein synthesis in rifampicin-inhibited normal and ethylenediaminetetraacetic acid (EDTA)-treated Escherichia coli was measured. Approximately 200-fold higher external concentrations of rifampicin were needed to produce a level of inhibition in normal cells comparable to that observed in EDTA-treated cells. The rates of RNA and protein synthesis in both kinds of cells decreased exponentially, after an initial lag phase, at all rifampicin concentrations tested. The lag phase was longer and the final exponential slope less for protein synthesis than for RNA synthesis at a given rifampicin concentration. Below certain rifampicin concentrations, both the lag phase and the subsequent exponential decrease in the rates of RNA and protein synthesis were found to be rifampicin concentration dependent. At greater concentrations only the time of the lag phase was decreased by higher rifampicin concentrations, whereas the slope of the exponential decrease in the rates of RNA and protein synthesis was unaffected. In all cases, the exponential decrease continued to at least a 99.8% inhibition of the original rate of synthesis. These in vivo results are consistent with the mode of rifampicin action determined from in vitro studies; rifampicin prevents initiations of RNA polymerase on deoxyribonucleic acid, but not its propagation, by binding the enzyme essentially irreversibly. The results also indicate the size distribution of messenger RNA molecules in E. coli under our conditions.

Bacterial Proteins↗
PubMed1968

T4 bacteriophage mutants suppressible by a missense suppressor which inserts glycine in place of arginine for the codon AGA.

Phage mutants of T4 have been isolated which can multiply only on Escherichia coli strains which contain a missense suppressor which is known to cause the substitution of glycine for arginine in response to the AGA codon. Mutations producing the suppressible phenotype were mapped and shown to occur in six different phage cistrons. Two of the cistrons were concerned with deoxyribonucleic acid synthesis, two were concerned with phage structural components, and two were concerned with functions required for growth in E. coli K-12 but not in E. coli B. The burst size of the different phage mutants grown on strains carrying the same suppressor was dependent upon the efficiency of suppression, which in turn is known to be dependent upon the glycyl-transfer ribonucleic acid synthetase activity.

Arginine↗